That’s different than what happened in 1999 and 2000, when the Fed raised its target rate for overnight loans between banks six times to 6.5 percent. Even with the policy, gains in gross domestic product have averaged 2 percent since 2009, less than half the rate as the 50 months through March 2000.

While the advance since 2009 that added $11.3 trillion to the value of stocks is comparable to the last four years of the technology bubble, it remains weaker than returns generated in that rally’s strongest stretch. The S&P 500’s level almost tripled during the 50 months starting in December 1994. Reaching gains of a similar size would have required the index to climb to about 1,918, or 17 percent above last week’s close.

Equal Weights

One version of the S&P 500 is posting returns that big. The so-called equal weighted index that strips out biases related to company value has surged 208 percent, or 31 percent annually, since March 2009, data compiled by Bloomberg show. It rose about half as much as the weighted S&P 500 during the 1996 to 2000 period.

Breadth has characterized the advance since 2009. About 89 percent of stocks in the benchmark index are trading above their average price from the past 50 days, compared with 65 percent on March 24, 2000, when the Internet bubble burst, data compiled by Bloomberg show. Only 27 stocks made a new 52-week high at the peak of the market in 2000, compared with 74 last week.

Encouraging Skepticism

“The bull market in 1999 and into early 2000 was increasingly narrow in terms of the number of companies driving the performance of the market,” Mark Luschini, chief investment strategist at Janney Montgomery Scott LLC in Philadelphia, which manages $55 billion, said in a May 8 phone interview. “You have not yet seen the level of euphoria you saw in 1999, when it was driving equity prices north of 30 times earnings,” he said. “That level of skepticism is encouraging from a contrarian standpoint.”

While valuations are 28 percent below the 1990s rally, low earnings multiples are also a sign that investors don’t trust the economy will grow fast enough to support analyst estimates of future profits. S&P 500 earnings rose 1.8 percent in the quarter ending March 31, more than 11,000 analyst estimates show. That compares with an average of 4.7 percent last year and 25 percent in 2010 and 2011, according to Bloomberg data.

“Even though the market’s up, there’s still a great deal of concern from investors,” Matt McCormick, who helps oversee $9.1 billion as a money manager at Cincinnati-based Bahl & Gaynor Inc., said in a May 9 phone interview. “It’s a situation where people really need to be selective.”

Defensive Rally